This information is for people affected by or concerned about Lennox-Gastaut syndrome, including parents and carers.
On this page we talk about how Lennox-Gastaut syndrome is diagnosed, what causes it, symptoms, treatment options and long-term outlook.
Use this page as a general guide and speak to a health professional for more information and support.
On this page
What is Lennox-Gastaut syndrome?
Lennox-Gastaut syndrome is a rare and severe type of epilepsy. Children diagnosed with this type of epilepsy usually experience multiple different seizure types, as well as learning difficulties which can range from mild to severe.
Most children with Lennox-Gastaut syndrome will have been diagnosed with a different form of epilepsy before being diagnosed with Lennox-Gastaut syndrome.
Who can get Lennox-Gastaut syndrome?
Lennox-Gastaut syndrome affects about one or two children in every 100 children.
The most common time for the syndrome to start is between the ages of three and five years. It affects slightly more boys than girls – the reason for this is unclear and more research is needed to understand why.
What causes Lennox-Gastaut syndrome?
In about one in four children, the cause of Lennox-Gastaut syndrome is unknown.
For other children with Lennox-Gastaut syndrome, causes may include:
- Brain damage following a head injury
- Problems just before or during birth, which cause a lack of oxygen to the brain (asphyxia)
- Problems with how the brain is formed during pregnancy
- Having certain infections as a baby, such as meningitis, encephalitis and rubella (german measles)
- Genetic conditions such as tuberous sclerosis
- A history of having Infantile spasms (known as West syndrome)
How is Lennox-Gastaut syndrome diagnosed?
Lennox-Gastaut syndrome is not always diagnosed quickly. For some people, getting a diagnosis may take years. This is because it might not be clear when seizures began. A specialist doctor may have to do lots of different tests and take a full medical history before they can say for sure whether a child has Lennox-Gastaut syndrome or not.
You may be referred to a paediatrician (a doctor who specialises in child health).
When taking a child’s medical history, the doctor will ask about any signs of previous seizures, especially infantile spasms.
The doctor may also ask you about any learning delays, hearing and sight problems, and if the child has had tuberous sclerosis.
The doctor may need to carry out some tests on the child. This will help them to build a clear picture of the child’s health and work out if they’re likely to have Lennox-Gastaut syndrome.
Tests may include:
- An EEG (electroencephalogram) test – a painless test that uses small sensors attached to the scalp to pick up the electrical signals produced by the brain.
- An MRI (magnetic resonance imaging) scan – a non-invasive scan that uses magnetic fields and radio waves to produce images from inside the body.
The EEG results will likely show a distinctive pattern while the child is awake and asleep.
Doctors might also carry out flashing light and hyperventilation (rapid breathing) tests during the EEG test.
They may also carry out blood or urine tests.
What are the different types of seizures?
Children with Lennox-Gastaut syndrome usually develop a range of other seizure types as they get older. These usually happen often, with some children having several seizures a day.
Types of seizures may include:
- Atonic seizures
- Absence seizures
- Tonic seizures
- Tonic-clonic seizures
- Focal onset seizures
- Myoclonic seizures
We describe each seizure type in more detail below.
Atonic seizures happen when one or both sides of the brain are affected. They are often called ‘drop attacks’. Atonic seizures are very short, usually lasting less than two seconds.
During atonic seizures, there is a sudden loss of muscle strength, which may cause the child to fall to the ground. This may cause injuries, especially if the child falls on their head or face.
Absence seizures happen when both sides of the brain are affected. There are two types of absence seizures:
- Typical absence seizures. During this type of seizure the child may suddenly stop what they are doing for a few seconds, but will not fall. They might appear to be daydreaming or ‘switching off’. Their eyelids might flutter or their limbs may make slight jerking movements. Typical absence seizures are very short but may happen several times a day.
- Atypical absence seizures. During this type of seizure, the child may still move around and their muscles might go limp or ‘floppy’. Atypical absence seizures can last for up to ten minutes. People who have atypical absence seizures might also have learning disabilities or other conditions that affect their brain.
If your child has tonic seizures, their arms and legs may stiffen, causing them to fall. Their eyes may also widen and roll upwards. There is usually no repetitive jerking. Tonic seizures can last from a few seconds to a few minutes.
These seizures usually happen during sleep. This means that sleep is disturbed and after a tonic seizure the child may be confused and sleepy.
During a tonic-clonic seizure, the child may lose consciousness, go rigid (stiff) and fall. This is then usually followed by repetitive jerking of the limbs.
Focal onset seizures occur in one area of the brain. The brain is divided into four parts known as lobes:
- Frontal lobes
- Occipital lobes
- Parietal lobes
- Temporal lobes
What happens during a focal onset seizure will depend on which section of the brain is affected. Symptoms can range from subtle sensory changes to more severe movements in the body and loss of consciousness.
Children who have myoclonic seizures usually experience sudden muscle jerks. Myoclonic seizures are brief but can happen in clusters (many happening close together in time), and often happen shortly after waking. These types of seizures usually stop once the child is about five years old.
Find out more about all of the above seizure types.
Are there any other signs or symptoms?
Most children with Lennox-Gastaut syndrome will experience delays in their development, these include behavioural and psychological problems.
Behavioural and psychological problems
Behavioural and psychological problems are common in children with Lennox-Gastaut syndrome, these may include:
- Hyperactivity
- Irritability
- Autistic behaviours
- Poor social skills
- Attention-seeking behaviour
It can be difficult to find out what causes these behaviours. They may result from ongoing abnormal electrical activity in the brain, the side effects of anti-seizure medications or difficulty understanding information. Talk to the child’s doctor if you’re worried about behavioural or psychological problems.
Treatments for Lennox-Gastaut syndrome
There is no cure for Lennox-Gastaut syndrome, but with the right medicine it can usually be managed and seizures can be controlled.
Remember that everyone is different and what works for one person might not work well for someone else. People with Lennox-Gastaut syndrome may have to try a few different medicines until something works well.
Talk to a doctor about treatment options and what might be suitable. They should explain the advantages and disadvantages of each treatment, including any possible side effects.
First treatment options
For people diagnosed with Lennox-Gastaut syndrome, the first recommended treatment is sodium valproate (also known as Epilim).
Sodium valproate comes as capsules, tablets or a liquid that you swallow. It also comes as granules that you mix with food or drink. It can also be given by injection, but this is usually only done in hospital or in emergencies.
Sodium valproate is recommended as the first treatment option because there’s not much good quality evidence that shows whether other treatments work as well.
However, sodium valproate may not suitable for everyone, including all women and girls. This is because sodium valproate may affect fertility (the ability to get pregnant naturally).
For women who can have children, and young girls who are likely to need treatment when they’re old enough to have children, a doctor should consider the following things before prescribing sodium valproate:
- The benefits and risks of sodium valproate, including any risks to an unborn child.
- The likelihood of pregnancy and if appropriate, a pregnancy prevention programme should be put in place.
Read more about the process for prescribing sodium valproate and how it can affect fertility.
Sodium valproate
In January 2024, new rules were introduced for prescribing sodium valproate.
Two specialists are now needed to approve:
- New or ongoing valproate treatments for girls and women.
- New valproate treatments for boys and men
The specialists must agree that your epilepsy does not respond to other treatments and the benefits of treatment outweigh the risks.
For girls and women, valproate can seriously harm an unborn baby when taken during pregnancy.
For boys and men, valproate may cause infertility. Some people’s fertility may return when their treatment is stopped or reduced. There is also some evidence that valproate can cause harm in the testicles of animals, but it’s unclear what this means for humans.
Never stop taking valproate before talking to your specialist first. Not taking medication as prescribed can increase the risk of a seizure.
Your epilepsy specialist will let you know when your treatment is due to be reviewed.
If you are planning a pregnancy it is important to speak to your healthcare professional as soon as possible about your treatment options.
If you have any questions or concerns about valproate, please speak to your healthcare professional.
Find out more about sodium valproate in the MHRA’s patient guide.
Find out more about Anti-seizure medications, contraception and pregnancy.
Second treatment options
If the first treatment option does not work, then lamotrigine (also known as Lamictal) can be tried on its own or as an add-on treatment option. Lamotrigine is a medicine that comes as a tablet that you swallow.
Third treatment options
If the second treatment does not work, your doctor may suggest trying the following add-on treatment options:
- Cannabidiol (also known as Epidyolex), a medicine that comes as a liquid that you swallow, combined with clobazam (also known as Frisium and Onfi), a medicine that comes as tablets or liquid that you swallow.
- Clobazam (also known as Frisium and Onfi) on its own.
- Rufinamide (also known as Inovelon) – a medicine that comes as a tablet that you swallow.
- Topiramate (also known as Topamax), a medicine that comes as a tablet that you swallow.
When these medicines are being used as add-on treatments alongside sodium valproate, the child’s doctor will carefully review the doses of each and check often for any side effects, including sedation (sleepiness).
Further treatment options
If seizures continue after the third treatment options have been tried, a ketogenic diet can be tried as an add-on treatment. This is a special type of diet that is high in fat and protein, but low in carbohydrates. It can work well at reducing the intensity and frequency of seizures. It must be supervised by a ketogenic diet team.
What’s the long-term outlook for Lennox-Gastaut Syndrome?
Managing seizures can be difficult at any age. But for babies and small children it can be especially challenging. The long-term outlook for children with Lennox-Gastaut syndrome varies from child to child.
The vast majority of children will continue to have seizures into adulthood and may never be able to live independently.
They will need continuing support with their learning and behavioural problems.
Living with Lennox-Gastaut syndrome and getting support
Lennox-Gastaut syndrome is a life-long form of epilepsy. It can be difficult and upsetting for parents or carers to manage a child’s learning difficulties as well as trying to control seizures.
Talk to the child’s doctor for help on how to support them well. And talk to your own doctor if you need support for yourself. If you’re caring for someone with Lennox-Gastaut syndrome, it’s important that you look after yourself and get the support you need.
You may find it helpful joining an in-person or online support group, where you can listen to or share experiences with other people who understand what you’re going through.
Other useful organisations
LGS Foundation
An American organisation that has information for people affected by Lennox-Gastaut syndrome.
